ISTANBUL , Turkey -LRB- CNN -RRB- -- It 's a common sight in the traffic-clogged streets of Istanbul , a city that straddles two continents .

Workers next to the spot where subway trains will one day emerge from the tunnel . Opening of the tunnel has been delayed by at least four years by the discovery .

A taxi driver , enraged by perpetually gridlocked traffic , stepping out of his car and yelling `` Maniac ! '' at the man driving the public bus behind him .

For decades Istanbul has been growing at a breakneck speed ; its population exceeding -- by some estimates -- 15 million people . Too bad traffic often moves at a snail 's pace .

Most residents are quick to tell visitors the city 's transport system is overwhelmed .

`` Istanbul is a dynamically changing city , every year increasing in population , '' says Zeynep Buket , an engineer working with Turkey 's transportation ministry . `` We are in need of radical systems , and this radical system is a mass transit system . ''

The `` radical system '' city planners embarked on five years ago involved construction of a new subway tunnel beneath the Bosphorus Strait , the spectacular body of water that cuts this city in two . By the year 2025 , engineers predict more than one million people a day will use the tunnel to travel between Istanbul 's Asian and European shores .

`` We will connect two continents , Asia and Europe , '' said Nusret Ilbay , one of the many engineers working on the $ 3 billion Marmaray Tunnel Project . He was standing on scaffolding , overlooking a gaping 30-meter deep hole that will one day be a subway station on the Asian side of the Bosphorus . A concrete wall is all that holds back a churning river of sea water . Watch video of the tunnel being constructed

`` As you can see , some leakage on the wall face has been observed , '' Ilbay explained on a tour of the construction site . `` In order to overcome these leakages , we have applied chemical grouting . ''

Legend has it , thousands of years ago Jason and the Argonauts narrowly escaped death sailing up the Bosphorus in search of the mythological Golden Fleece .

Today , engineers face equally daunting challenges building a tunnel beneath one of the world 's busiest shipping channels , at depths of up to 55 meters , in an active earthquake zone .

First they dredged a trench on the bottom of the Bosphorus . Then , using divers and undersea cameras , they submerged and buried 11 massive pre-fabricated tunnel segments , almost all of them longer than a football field .

To enter the unfinished tunnel , visitors must climb down a steep staircase in a construction tower surrounded by water in the middle of the strait . During the descent , the temperature plummets and humidity rises .

Construction workers toil here in the gloom of this 1.4 kilometer long tube on the bottom of the sea , their welding torches spraying showers of sparks in the darkness .

One worker claimed that during the lunch break , when the machinery came to a stop , he could hear the sound of oil tanker and cargo ships ' engines as they motored past in the waters overhead .

As a precaution in the event of a catastrophic flood in the tunnel , engineers constructed an emergency bunker on the bottom of the sea . Stocked with food and water and equipped with a heavy water-proof door , the `` emergency room '' is supposed to protect survivors for up to 10 days , until they can be rescued .

But , in their rush to modernize Istanbul 's transport system , city planners ran into an unforeseen obstacle : history .

In Yenikapi , a neighborhood of textile factories and seedy hotels where one of the main transit stations for Istanbul 's new subway and commuter rail system was to be built , archaeologists discovered the lost Byzantine port of Theodosius .

It was originally built at the end of the 4th century AD by Emperor Theodosius I when Istanbul -- then known as Constantinople -- was the capital of the eastern Roman Empire . The port 's harbor silted over centuries ago , and eventually disappeared beneath subsequent layers of civilization . Until its rediscovery in 2004 , archaeologists said they only knew about the port from ancient books .

`` This was a big moment of joy and happiness for us , an unexplainable feeling , '' recalls Professor Zeynep Kiziltan , the acting director of Istanbul 's Archaeology Museum . Look at pictures of the excavation ''

`` At around one meter below sea level , we started finding the remains of ropes . As we continued -LSB- digging -RSB- a bit more , the remains of a boat surfaced . ''

Since that discovery , armies of hundreds of laborers and archaeologists have been working in a giant pit , three shifts a day , seven days a week . The scale of the excavation is unusual in modern-day archaeology , says Cemal Pulak , an anthropologist from Texas A&M University 's nautical archaeology program . Look at a map of the site

`` Its mind-boggling ... it really looks like an Indiana Jones-type operation , '' says Pulak , who has worked as a consultant on the excavation of the lost port .

The Yenikapi dig has uncovered an ancient armada : 34 Byzantine ships ranging from dating between the 7th and 11th centuries AD .

In one tent , two workers carefully uncover the ancient wooden beams of a 40-meter long merchant vessel . A third man preserves the wood by keeping it moist , sprinkling the relics with water from a hose .

Archaeologists have nicknamed this ship `` The Titanic , '' because it is the largest of the Theodosius wrecks . It is believed the vessel once carried wheat from Egypt to Constantinople . Scattered around the ship are shards of pottery , animal bones , and thousand-year-old clamshells .

Historians say the new discoveries include the first examples of ships being built using the beginnings of the `` skeleton approach '' to constructing the vessel 's hull . Pulak says that marked a revolutionary change which transformed shipbuilding from `` mostly an art form to a science . ''

`` The earlier methods of building depended on verbal transference of the method from master shipbuilders to apprentices , '' he explained . `` The development of the latter method ... allowed for the speedy communication of new shipbuilding ideas that could be transmitted on paper . It is the beginning of engineering . Ships could be preconceived and pre-designed . ''

`` I think it is one of the unique projects not only for us but for the world , '' said geologist Yucel Yilmaz .

In addition to finding the timbers of thousand-year-old jetties and docks , which still jut up in straight rows at the bottom of the mammoth pit , archaeologists have uncovered the remnants of a pre-historic human settlement .

`` The first man , about 8,400 years ago , came and started to settle here , '' Yilmaz said . `` There was no Bosphorus -LSB- then -RSB- . The Bosphorus was a river valley ... the people who settled here walked across the Bosphorus . ''

Plans to travel beneath the Bosphorus have been delayed at least four years by the excavation of the Theodosious Port . The postponement has added untold millions of dollars have also been added to the cost of the entire project .

In the rush to move forward , the residents of Istanbul have accidentally uncovered a valuable piece of their city 's ancient past .

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A 1.4 km long subway tunnel is being constructed under Istanbul 's Bosphorus Strait

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Operation uncovered the lost 4th century AD Byzantine port of Theodosius

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Thirty-four 1000-year-old ships have been excavated as well as remains of the port

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Discovery has delayed tunnel project by at least four years costing millions of dollars